fix(language-service): infer context type of structural directives (#35537) (#35561)

PR Close #35561

packages/language-service/src/expression_diagnostics.ts

@@ -91,7 +91,10 @@ function getVarDeclarations(
       continue;
     }
     for (const variable of current.variables) {
-      let symbol = info.members.get(variable.value) || info.query.getBuiltinType(BuiltinType.Any);
+      let symbol = info.members.get(variable.value);
+      if (!symbol) {
+        symbol = getVariableTypeFromDirectiveContext(variable.value, info.query, current);
+      }
       const kind = info.query.getTypeKind(symbol);
       if (kind === BuiltinType.Any || kind === BuiltinType.Unbound) {
         // For special cases such as ngFor and ngIf, the any type is not very useful.
@@ -115,22 +118,24 @@ function getVarDeclarations(
 }
 
 /**
- * Gets the type of an ngFor exported value, as enumerated in
+ * Resolve the type for the variable in `templateElement` by finding the structural
- * https://angular.io/api/common/NgForOfContext
+ * directive which has the context member. Returns any when not found.
- * @param value exported value name
+ * @param value variable value name
  * @param query type symbol query
+ * @param templateElement
  */
-function getNgForExportedValueType(value: string, query: SymbolQuery): Symbol|undefined {
+function getVariableTypeFromDirectiveContext(
-  switch (value) {
+    value: string, query: SymbolQuery, templateElement: EmbeddedTemplateAst): Symbol {
-    case 'index':
+  for (const {directive} of templateElement.directives) {
-    case 'count':
+    const context = query.getTemplateContext(directive.type.reference);
-      return query.getBuiltinType(BuiltinType.Number);
+    if (context) {
-    case 'first':
+      const member = context.get(value);
-    case 'last':
+      if (member && member.type) {
-    case 'even':
+        return member.type;
-    case 'odd':
-      return query.getBuiltinType(BuiltinType.Boolean);
       }
+    }
+  }
+  return query.getBuiltinType(BuiltinType.Any);
 }
 
 /**
@@ -145,6 +150,7 @@ function getNgForExportedValueType(value: string, query: SymbolQuery): Symbol|un
 function refinedVariableType(
     value: string, mergedTable: SymbolTable, query: SymbolQuery,
     templateElement: EmbeddedTemplateAst): Symbol {
+  if (value === '$implicit') {
     // Special case the ngFor directive
     const ngForDirective = templateElement.directives.find(d => {
       const name = identifierName(d.directive.type);
@@ -153,22 +159,20 @@ function refinedVariableType(
     if (ngForDirective) {
       const ngForOfBinding = ngForDirective.inputs.find(i => i.directiveName == 'ngForOf');
       if (ngForOfBinding) {
-      // Check if the variable value is a type exported by the ngFor statement.
+        // Check if there is a known type for the ngFor binding.
-      let result = getNgForExportedValueType(value, query);
-
-      // Otherwise, check if there is a known type for the ngFor binding.
         const bindingType = new AstType(mergedTable, query, {}).getType(ngForOfBinding.value);
-      if (!result && bindingType) {
+        if (bindingType) {
-        result = query.getElementType(bindingType);
+          const result = query.getElementType(bindingType);
-      }
-
           if (result) {
             return result;
           }
         }
       }
+    }
+  }
 
   // Special case the ngIf directive ( *ngIf="data$ | async as variable" )
+  if (value === 'ngIf') {
     const ngIfDirective =
         templateElement.directives.find(d => identifierName(d.directive.type) === 'NgIf');
     if (ngIfDirective) {
@@ -180,6 +184,7 @@ function refinedVariableType(
         }
       }
     }
+  }
 
   // We can't do better, return any
   return query.getBuiltinType(BuiltinType.Any);

packages/language-service/test/diagnostics_spec.ts

@@ -286,6 +286,42 @@ describe('diagnostics', () => {
       expect(start).toBe(span.start);
       expect(length).toBe(span.length);
     });
+
+    it('report an unknown field in $implicit context', () => {
+      mockHost.override(TEST_TEMPLATE, `
+        <div *withContext="let myVar">
+          {{ ~{start-emb}myVar.missingField ~{end-emb}}}
+        </div>
+      `);
+      const diags = ngLS.getSemanticDiagnostics(TEST_TEMPLATE);
+      expect(diags.length).toBe(1);
+      const {messageText, start, length, category} = diags[0];
+      expect(category).toBe(ts.DiagnosticCategory.Error);
+      expect(messageText)
+          .toBe(
+              `Identifier 'missingField' is not defined. '{ implicitPerson: Person; }' does not contain such a member`, );
+      const span = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'emb');
+      expect(start).toBe(span.start);
+      expect(length).toBe(span.length);
+    });
+
+    it('report an unknown field in non implicit context', () => {
+      mockHost.override(TEST_TEMPLATE, `
+        <div *withContext="let myVar = nonImplicitPerson">
+          {{ ~{start-emb}myVar.missingField ~{end-emb}}}
+        </div>
+      `);
+      const diags = ngLS.getSemanticDiagnostics(TEST_TEMPLATE);
+      expect(diags.length).toBe(1);
+      const {messageText, start, length, category} = diags[0];
+      expect(category).toBe(ts.DiagnosticCategory.Error);
+      expect(messageText)
+          .toBe(
+              `Identifier 'missingField' is not defined. 'Person' does not contain such a member`, );
+      const span = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'emb');
+      expect(start).toBe(span.start);
+      expect(length).toBe(span.length);
+    });
   });
 
   // #17611

packages/language-service/test/project/app/main.ts

@@ -43,6 +43,7 @@ import * as ParsingCases from './parsing-cases';
     ParsingCases.StringModel,
     ParsingCases.TemplateReference,
     ParsingCases.TestComponent,
+    ParsingCases.WithContextDirective,
   ]
 })
 export class AppModule {

packages/language-service/test/project/app/parsing-cases.ts

@@ -127,6 +127,21 @@ export class CounterDirective implements OnChanges {
   }
 }
 
+interface WithContextDirectiveContext {
+  $implicit: {implicitPerson: Person;};
+  nonImplicitPerson: Person;
+}
+
+@Directive({selector: '[withContext]'})
+export class WithContextDirective {
+  constructor(_template: TemplateRef<WithContextDirectiveContext>) {}
+
+  static ngTemplateContextGuard(dir: WithContextDirective, ctx: unknown):
+      ctx is WithContextDirectiveContext {
+    return true;
+  }
+}
+
 /**
  * This Component provides the `test-comp` selector.
  */